Insect development is under genetic and hormonal control. Two hormones, juvenile hormone and ecdysone control and dynamic changes that occur between various stages when entire sets of genes are turned "on" or "off" in succession. Since these changes are acquisitions of new functions suited for different modes of life, the changes are presumably due to the induction or preferential synthesis of new proteins. The precise mechanisms by which these hormones control insect metamorphosis remains to be established. The assumptions behind many of the studies related to hormonal function in insects appear to be (a) There exist different genes (sets) specifying larval, pupal and adult stages and (b) These genes (sets) are turned "on" and "off" in succession by the interaction of the two hormones. The present proposal aims at answering the following questions: 1) Are there different sets of genes corresponding to the different stages of development which are expressed as mRNAs and which are in turn translated into identifiable polypeptide products; and 2) how does the JH modify or control ecdysone action? These questions will be answered by comparing the poly A containing mRNA populations of insect tissues ideally suited for this purpose at different developmental stages and under varying hormonal treatments as to their (a) capacity to be translated in vitro to identifiable polypeptide components; (b) complexity and abundance of mRNA sequences common to and different from each other; and (c) similarity to RNA transcripts produced in vitro from isolated nuclei. The mRNAs will be translated in the wheat germ and reticulocyte cell free systems and compared by analyzing the kinetics of hybridization to DNA. Nucleic acid hybridizations will be carried out under two conditions, (1) in DNA excess and (2) in RNA excess.